Building machines of different designs are known for civil engineering projects both above and below ground. For building roads, self-propelling road-building machines are used which are distinguished by the fact that they have a chassis and running gear. The chassis is fitted with a working unit which has one or more implements. In this context, working unit is to be understood as the device with which the work which is necessary to build the road can be carried out. For this purpose, the working unit has one or more implements with which the individual working steps which are necessary to build the road can be carried out.
Road-building machines are, for example, road milling machines which economically remove damage to road surface coverings. The road milling machines have, for this purpose, a milling device, for example a milling roller with milling cutters, and a conveyor device for feeding the milled-away road surface covering. The running gear of the road miller can have sets of wheels or caterpillar tracks.
In order to control the implements of the working unit, the known building machines generally have a stored-program controller, which is an electronic assembly which is used in automation technology for open-loop and closed-loop control functions. The stored-program control device has inputs and outputs and a memory for a program according to which the open-loop and closed-loop control functions are carried out.
In addition to the stored-program control device, the known building machines generally have a device for sensing operational variables or operational states which include, for example, the oil pressure or the coolant temperature of the diesel engine for driving the building machine, or in the case of a road milling machine, for example the advancing speed and the position of the milling roller with which the milling depth is predefined. In order to sense the operational variables or operational states, the device has, for example, pressure sensors, temperature sensors, position switches or limit switches, rotational speed signal transmitters or the like, whose analogue or digital signals are applied as input signals to the input of the stored-program control device. The signals for controlling, for example pneumatic or hydraulic valves, mechanical or electrical switches or the like, with which in turn the implements of the working unit are controlled, are present at the output of the control device as output signals.
Furthermore the building machines have a device for inputting operational variables or operational states, for example the desired advancing speed of the building machine. The input device can comprise various switches and a keyboard which are arranged on an operator control panel at an operator control location on the building machine.
In addition to the input device, the building machines have a device for displaying operational variables or operational states in the form of characters or images in order to inform the operator continuously about the operational variables or operational states.
The display of the operational variables or operational states in the form of characters or images takes place in the known building machines in such a way that the output signals of the stored-program control device which are relevant to the operational parameters or operational states are transmitted via a data bus to the operator control location at which the signals which are necessary for the display in the form of characters or images and which are displayed on a monitor are obtained from said output signals.
The devices for displaying characters or images of the known building machines are information systems which display operational variables or operational parameters in graphic form, for example with bar graphs or pictograms (icons). The bar graphs and pictograms are displayed in the known devices in pixels, in which case the display is monochrome. The known devices have the hardware and software which is necessary for the display of the bar graphs and pictograms. The relatively complex programming of the pixel display is carried out at the works end, but can also be modified by the customer.